US11742976B2 - Optical branch insertion device and optical transmission system using optical branch insertion device - Google Patents

Optical branch insertion device and optical transmission system using optical branch insertion device Download PDF

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US11742976B2
US11742976B2 US17/438,693 US202017438693A US11742976B2 US 11742976 B2 US11742976 B2 US 11742976B2 US 202017438693 A US202017438693 A US 202017438693A US 11742976 B2 US11742976 B2 US 11742976B2
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optical
wavelength
transponder
optical signal
cawg
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US20220149968A1 (en
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Masahiro Nakagawa
Kana MASUMOTO
Hidetoshi ONDA
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Nippon Telegraph and Telephone Corp
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Nippon Telegraph and Telephone Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/27—Arrangements for networking

Definitions

  • the present invention relates to an optical add/drop multiplexer used for light wavelength multiplexing or wavelength division multiplexing (WDM) in a communication network and configured to drop and add an optical signal transmitted through an optical fiber, and a light transmission system using the optical add/drop multiplexer.
  • WDM wavelength division multiplexing
  • the connection form of a communication network has evolved from a point-to-point (P2P) connection form, a ring connection form, a multi-the ring connection form, and a mesh connection form.
  • the P2P connection form is a form in which nodes as light transmission devices each configured to terminate communication data and relay the communication data to a communication terminal are oppositely connected with each other in a one-to-one state through an optical fiber.
  • the ring connection form is a form in which a plurality of nodes are connected with one another in a ring shape through an optical fiber.
  • the multi-the ring connection form is a form in which a plurality of rings in ring connection are connected with each other through nodes by optical fibers, and is included in mesh connection to be described later.
  • the mesh connection form is a form in which nodes are connected in mesh with one another through optical fibers to perform mutual communication therebetween.
  • OADM optical add/drop multiplexer
  • optical add/drop multiplexer examples include a CDC (colorless, directionless, and contentionless)-ROADM (reconfigurable optical add/drop multiplexer) having high functionality with the three functions of a first function, a second function, and a third function to be described later.
  • the CDC-ROADM enables remote reconstruction of an optical layer.
  • the ROADM is a function to enable add/drop of an optical signal at each node.
  • the CDC is a function (CDC function) to connect an optical signal added/dropped in a multi-path ROADM to a transponder (optical relay) without signal collision irrespective of a wavelength and a path.
  • a color-less function as the first function is a function with which an optical signal from a transponder can be output to the same path at an optional wavelength without change of physical wiring.
  • a direction-less function as the second function is a function with which an optical signal from a transponder can be output at an optional path without change of physical wiring.
  • a contention-less function as the third function is a function with which output to a path different from an existing path (existing transmission path) can be performed at the same wavelength from different transponders without change of physical wiring.
  • Non-Patent Literature 1 Examples of a light transmission system using such an optical add/drop multiplexer include a technology disclosed in Non-Patent Literature 1.
  • the CDC-ROADM used as the optical add/drop multiplexer described above uses a large number of active devices such as a multicast switch configured to perform switching when data is transferred from one transmission source to a plurality of destinations and an amplifier.
  • the present invention is intended to solve the above-described problem and provide an optical add/drop multiplexer having reduced device cost and electric power consumption and a light transmission system using the optical add/drop multiplexer.
  • an invention according to claim 1 is an optical add/drop multiplexer configured to drop or add an optical signal between the optical add/drop multiplexer and a transponder connected with a communication terminal, the optical signal being transmitted by wavelength division multiplexing to a light transmission path included in a communication network
  • the optical add/drop multiplexer includes a cyclic arrayed waveguide grating (cAWG) that includes a plurality of first side ports and a plurality of second side ports connected between the transponder and the light transmission path and in which a first channel interval of each of the first and second side ports is a plurality of times larger than a second channel interval of an optical signal input to and output from the transponder and optical signals of a plurality of different wavelengths from one or a plurality of the transponders or the light transmission path can pass or transmit through a first channel
  • the cAWG causes an optical signal output from each transponder to pass through the first channel at one of the first side ports, outputs and transmit
  • transponder signals of a plurality of different wavelengths can pass through channels at the first and second side ports of the cAWG.
  • the cAWG causes an optical signal from the transponder to pass through the first channel at the first side ports, and outputs and transmits the passing optical signal to the light transmission path in a cyclic relation determined in accordance with a corresponding first side port among the plurality of second side ports and the wavelength of the output optical signal from the transponder.
  • the optical signal transmitted the light transmission path can be caused to pass through the first channel at one of the second side ports, and the passing optical signal can be output to the transponder in a cyclic relation determined in accordance with the first side port among the plurality of first side ports and the wavelength of the output optical signal from the transponder.
  • the optical add/drop multiplexer of the present invention does not use a multicast switch nor an amplifier configured to compensate light loss, which leads to reduction of device cost and electric power consumption thereof.
  • An invention according to claim 2 is the optical add/drop multiplexer according to claim 1 , further including an optical switch (SW) unit configured to transmit or cut off, when the light transmission path includes a different light transmission path, an optical signal between the different light transmission path and the cAWG, and when the wavelength of a transponder signal as an optical signal from each transponder is changed to a different wavelength, the light SW unit transmits the transponder signal of the changed wavelength to the different light transmission path.
  • SW optical switch
  • an optical signal from the transponder can be output through an optional path, in other words, a different path without change of physical wiring between the optical add/drop multiplexer and the transponder device.
  • An invention according to claim 3 is the optical add/drop multiplexer according to claim 2 in which when a plurality of the cAWGs and a plurality of the transponders are provided, the light SW unit transmits, to different light transmission paths, transponder signals having an identical wavelength, transmitted from different transponders, and having passed through the first channels at different cAWGs.
  • output to a path different from an existing path can be performed at the same wavelength from different transponders without change of physical wiring between the optical add/drop multiplexer and the transponder device.
  • An invention according to claim 4 is the optical add/drop multiplexer according to any one of claims 1 to 3 in which a 1 ⁇ N optical coupler that includes a port connectable with a port of the cAWG and includes ports connectable with a plurality of the transponders is connected between the cAWG and the transponder, and an optical amplifier is connected between the cAWG and the 1 ⁇ N optical coupler.
  • the 1 ⁇ N optical coupler can be connected with N transponders, and thus the number of transponders connectable with the cAWG can be increased. In this case, a signal loss through N drops at the 1 ⁇ N optical coupler can be canceled through signal amplification at the optical amplifier.
  • An invention according to claim 5 is the optical add/drop multiplexer according to claim 2 or 3 in which the light SW unit includes a wavelength selective switch (WSS) configured to perform multiplexing-demultiplexing of the wavelength of an optical signal transmitted to the light transmission path and path switching of the optical signal, and the cAWG is connected in parallel with the WSS.
  • WSS wavelength selective switch
  • an additional cAWG can be connected in parallel with the WSS, and thus another transponder can be connected with the additional cAWG. Accordingly, the number of connectable transponders can be increased.
  • An invention according to claim 6 is the optical add/drop multiplexer according to any one of claims 1 to 3 , further including a 1 ⁇ N optical coupler that includes a port connected with the cAWG, includes ports connectable with a plurality of the transponders, and is connected between the cAWG and the transponder, N ports of the 1 ⁇ N optical coupler are connected with a multi carrier optical path transponder including a plurality of transmission ports and a plurality of reception ports, and the optical coupler or the 1 ⁇ N optical coupler is connected with a single carrier optical path transponder.
  • a 1 ⁇ N optical coupler that includes a port connected with the cAWG, includes ports connectable with a plurality of the transponders, and is connected between the cAWG and the transponder, N ports of the 1 ⁇ N optical coupler are connected with a multi carrier optical path transponder including a plurality of transmission ports and a plurality of reception ports, and the optical coupler or the 1 ⁇ N optical coupler is connected with a
  • a single carrier optical path and a multi carrier optical path can be provided in mixture.
  • a multi carrier optical signal in which optical signals having a plurality of kinds of wavelengths are superimposed is transmitted from the multi carrier optical path transponder, a signal having a larger number of wavelengths can be input to an identical AWG port, and thus large-volume data transmission can be performed through one path.
  • An optical signal transmitted from the multi carrier optical path transponder connected with the N ports of the 1 ⁇ N optical coupler may be divided into optical signals having a plurality of kinds of wavelengths, and the divided optical signals may be transmitted to different light transmission paths.
  • the number of optical signals superimposed in one multi carrier optical signal is smaller, but data transmission can be performed through a plurality of systems when the transmission is performed through different light transmission paths.
  • An invention according to claim 7 is a light transmission system including: the optical add/drop multiplexer according to any one of claims 1 to 6 ; and a monitoring control device separately connected with the optical add/drop multiplexer and configured to instruct optical path generation control and wavelength change control to the optical add/drop multiplexer, and the optical add/drop multiplexer includes a monitoring control unit configured to perform the instructed optical path generation control and wavelength change control to generate an optical path and change the wavelength of an optical signal in the optical add/drop multiplexer.
  • the wavelength of an optical signal transmitted from a transponder can be changed to a different wavelength under remote control by the monitoring control device without change of physical wiring between the optical add/drop multiplexer and the transponder device.
  • An invention according to claim 8 is the light transmission system according to claim 7 in which the optical add/drop multiplexer includes an optical coupler connected with a light transmission path and configured to bifurcate or connect an optical signal, and an optical amplifier connected with an input-output side of the optical coupler, and when input power of the optical amplifier or the number of wavelength of an input optical signal deviates by a predetermined value or more from input power or the number of wavelength of an input optical signal at path generation control, which is instructed by the monitoring control device, the monitoring control unit performs control to stop output from a transponder that transmits and receives optical signals to and from the optical coupler.
  • optical add/drop multiplexer having reduced device cost and electric power consumption and a light transmission system using the optical add/drop multiplexer.
  • FIG. 1 is a block diagram illustrating the configuration of a light transmission system using an optical add/drop multiplexer according to an embodiment of the present invention.
  • FIG. 2 is an explanatory diagram of functions (characteristics) of a cAWG.
  • FIG. 3 is a diagram illustrating the waveform of a wavelength corresponding to the channel interval of ports of the cAWG and the waveform of a wavelength corresponding to the channel interval of ports at a transponder.
  • FIG. 4 is a diagram illustrating the wavelengths of optical signals output from three output ports of the cAWG illustrated in FIG. 2 .
  • FIG. 5 is a block diagram illustrating the configuration of a monitoring control device in a light transmission system of the present embodiment.
  • FIG. 6 is a block diagram illustrating the number of each link between connected nodes and the use state of each wavelength in the light transmission system of the present embodiment.
  • FIG. 7 is a diagram illustrating a table configuration of a wavelength use management table stored in a DB in the monitoring control device in the light transmission system of the present embodiment.
  • FIG. 8 is a block diagram illustrating another configuration of the monitoring control device in the light transmission system of the present embodiment.
  • FIG. 9 is a block diagram illustrating specific configurations of a light SW unit and an add/drop unit in the light transmission system of the present embodiment.
  • FIG. 10 is a block diagram illustrating other specific configurations of the light SW unit and the add/drop unit in the light transmission system of the present embodiment.
  • FIG. 11 is a block diagram illustrating a first port number increasing configuration of an add unit or drop unit including a cAWG and an optical coupler in the add/drop unit in the light transmission system of the present embodiment.
  • FIG. 12 is a block diagram illustrating a second port number increasing configuration of the add unit or the drop unit with a cAWG in the add/drop unit in the light transmission system of the present embodiment.
  • FIG. 13 is a diagram illustrating the relation between a port input-output signal wavelength (reference wavelength) for a 1 ⁇ N add unit in existing connection and a port input-output signal wavelength (target wavelength) of a 1 ⁇ N add unit in additional connection in parallel in the add/drop unit in the light transmission system of the present embodiment.
  • FIG. 14 is a block diagram illustrating a mixed configuration of a single carrier optical path and a multi carrier optical path in the light transmission system of the present embodiment.
  • FIG. 15 is a diagram illustrating the wavelength of a multi carrier optical signal output from a multi carrier optical path transponder.
  • FIG. 16 is a block diagram illustrating the configuration of a guard function and a monitoring function in the light transmission system of the present embodiment.
  • FIG. 1 is a block diagram illustrating the configuration of a light transmission system using an optical add/drop multiplexer according to the embodiment of the present invention.
  • This light transmission system 10 illustrated in FIG. 1 has a configuration in which nodes 11 a , 11 b , 11 c , and 11 d as the optical add/drop multiplexers are connected with one another in a ring shape through optical fibers 12 and 13 as two light transmission paths.
  • Data can be transmitted through the optical fibers 12 and 13 in opposite directions or an identical direction, for example, in the clockwise direction (direction of an arrow Y 1 ) as an active system and/or the counterclockwise direction (direction of an arrow Y 2 ) as a redundant system.
  • the nodes 11 a to 11 d each have an identical configuration including a monitoring control unit 21 , optical amplifiers 22 a and 22 b , an optical switch (SW) unit 23 , an add/drop unit 24 , and a plurality of transponders 25 a , 25 b , . . . , and 25 n as illustrated representatively with the node 11 a .
  • the monitoring control unit 21 is connected with an external monitoring control device 15 configured to monitor and control the corresponding one of the nodes 11 a to 11 d .
  • the transponders 25 a , 25 b , . . . , and 25 n are connected with external communication terminals 31 a , 31 b , . . . , and 31 n such as personal computers.
  • FIG. 1 illustrates a configuration in which each transponder (for example, the transponder 25 a ) is connected with one communication terminal 31 a , but the one transponder 25 a may be connected with a plurality of communication terminals 31 a.
  • each transponder for example, the transponder 25 a
  • the one transponder 25 a may be connected with a plurality of communication terminals 31 a.
  • the add/drop unit 24 includes a plurality (two) of cyclic arrayed waveguide gratings (cAWGs) 24 a and 24 b .
  • the cAWGs 24 a and 24 b each have an input-output side port configuration of K input-outputs ⁇ N input-outputs (expressed as K ⁇ N), including K ports p 01 , . . . , and p 0 k on the K input-output side and N ports p 1 , p 2 , p 3 , p 4 , . . . , and pn on the N input-output side.
  • the ports p 1 to pn on the N input-output side are also referred to as first side ports p 1 to pn, and the ports p 01 to p 0 k on the K input-output side are also referred to as second side ports p 01 to p 0 k.
  • the second side ports p 01 and p 0 k of the cAWG 24 a are connected with the optical fibers 12 and 13 through the light SW unit 23
  • the first side port p 2 is connected with a port of the transponder 25 b
  • the second side ports p 01 and p 0 k of the cAWG 24 b are connected with the optical fibers 13 and 12 through the light SW unit 23
  • the first side port p 3 is connected with another port of the transponder 25 b.
  • FIG. 2 representatively illustrates the cAWG 24 a as a description target
  • the second side ports p 01 to p 03 are three ports
  • the first side ports p 1 to p 3 are three ports.
  • the first side ports p 1 to p 3 are connected with any three of the transponders 25 a to 25 n
  • the second side ports p 01 to p 03 are connected with any of the optical fibers 12 and 13 through the light SW unit 23 ( FIG. 1 ).
  • bands of wavelengths ⁇ a 1 , ⁇ a 2 , and ⁇ a 3 of frequencies different from one another are allocated to the first side port p 1 in a lateral direction illustrated with an arrow Y 11 .
  • the band of the wavelength ⁇ a 1 is allocated to the second side port p 01
  • the band of the wavelength ⁇ a 2 is allocated to the second side port p 02
  • the band of the wavelength ⁇ a 3 is allocated to the third side port p 03 .
  • bands of wavelengths ⁇ b 1 , ⁇ b 2 , and ⁇ b 3 as bands different from one another are allocated to the first side port p 2 .
  • the band of the wavelength ⁇ b 3 is allocated to the second side port p 01
  • the band of the wavelength ⁇ b 1 is allocated to the second side port p 02
  • the band of the wavelength ⁇ b 2 is allocated to the third side port p 03 .
  • bands of wavelengths ⁇ c 1 , ⁇ c 2 , and ⁇ c 3 as bands different from one another are allocated to the first side port p 3 .
  • the band of the wavelength ⁇ c 2 is allocated to the second side port p 01
  • the band of the wavelength ⁇ c 3 is allocated to the second side port p 02
  • the band of the wavelength ⁇ c 1 is allocated to the third side port p 03 .
  • AWG transmission bands of the first side ports p 1 to p 3 and the second side ports p 01 to p 03 of the cAWG 24 a are bandwidths f 1 to f 9 , bandwidths f 9 to f 17 , and bandwidths f 17 to f 25 of three wavelengths (also referred to as cAWG wavelengths) ⁇ a 1 , ⁇ a 2 , and ⁇ a 3 .
  • the bandwidth of one wavelength ⁇ c 1 is m times (a plurality of times or multiples) as large as a bandwidth corresponding to an optical signal input-output channel interval at a port of each of the transponders 25 a to 25 n .
  • Optical signals input to and output from the transponders 25 a to 25 n are also referred to as transponder signals.
  • the channel interval of the cAWG 24 a corresponds to a first channel interval described in the claims.
  • the channel interval of each transponder corresponds to a second channel interval described in the claims.
  • the bandwidth (in other words, filter passband) of each of the cAWG wavelengths ⁇ a 1 to ⁇ a 3 is, for example, 4 ⁇ jGHz, which is four times larger than a bandwidth jGHz of a transponder wavelength ⁇ 8 as representatively illustrated with the waveform of the cAWG wavelength ⁇ a 3 .
  • the bandwidth of the cAWG wavelength ⁇ a 1 includes transponder signal bandwidths of three different wavelengths ⁇ 1 to ⁇ 3
  • the bandwidth of the cAWG wavelength ⁇ a 2 includes transponder signal bandwidths of three different wavelengths ⁇ 4 to ⁇ 6
  • the bandwidth of the cAWG wavelength ⁇ a 3 includes transponder signal bandwidths of three different wavelengths ⁇ 7 to ⁇ 9 .
  • the channel interval of the cAWG wavelengths ⁇ a 1 to ⁇ a 3 is 4 ⁇ jGHz, which is representatively illustrated between a central frequency f 5 of the wavelength ⁇ a 1 and a central frequency f 13 of the wavelength ⁇ a 2 .
  • the channel interval 4 ⁇ jGHz is four times larger than a channel interval jGHz between the central frequency f 5 of a transponder wavelength ⁇ 2 and a central frequency f 7 of a transponder wavelength ⁇ 3 .
  • the cAWG 24 a has a function to regularly and cyclically output, through the second side ports p 01 , p 02 , and p 03 , transponder signals input through the first side port p 1 and having passed (or transmitted) through the bandwidths of the three wavelengths ⁇ a 1 to ⁇ a 3 . This is same for the other ports.
  • the cAWG 24 a has a function to regularly and cyclically output, through the band of the wavelength ⁇ a 1 of the first side port p 1 , optical signals input through the second side port p 01 and having passed through the bandwidths of the three wavelengths ⁇ a 1 , ⁇ b 3 , and ⁇ c 2 , output the optical signals through the band of the wavelength ⁇ b 3 of the first side port p 2 , and output the optical signals through the band of the wavelength ⁇ c 2 of the first side port p 3 .
  • the bandwidths of cAWG wavelengths output from the second side ports p 01 to p 03 of the cAWG 24 a illustrated in FIG. 2 are illustrated in FIG. 4 and described below.
  • Transponder wavelengths that can pass through the bandwidths of the cAWG wavelengths ⁇ a 1 to ⁇ a 3 input to the first side port p 1 illustrated in FIG. 2 are ⁇ 1 to ⁇ 9 illustrated in FIG. 3 . It is assumed that transponder wavelengths that can pass through the bandwidths of the cAWG wavelengths ⁇ b 1 to ⁇ b 3 of the first side port p 2 in FIG. 2 are a set of ⁇ 11 , ⁇ 12 , and ⁇ 13 , a set of ⁇ 14 , ⁇ 15 , and ⁇ 16 , and a set of ⁇ 17 , ⁇ 18 , and ⁇ 19 , respectively.
  • transponder wavelengths that can pass through the bandwidths of the cAWG wavelengths ⁇ c 1 to ⁇ c 3 of the first side port p 3 are a set of ⁇ 21 , ⁇ 22 , and ⁇ 23 , a set of ⁇ 24 , ⁇ 25 , and ⁇ 26 , and a set of ⁇ 27 , ⁇ 28 , and ⁇ 29 , respectively.
  • the bandwidths of the cAWG wavelengths of the second side port p 01 of the cAWG 24 a are disposed in the order of ⁇ a 1 , ⁇ c 2 , and ⁇ b 3 on the axis of a frequency f as follows. Specifically, the wavelength ⁇ a 1 through which the transponder wavelengths ⁇ 1 to ⁇ 3 can pass is disposed across the band of the frequencies f 1 to f 9 . The wavelength ⁇ c 2 through which the transponder wavelengths ⁇ 24 to ⁇ 26 can pass is disposed across the band of the frequencies f 9 to f 17 . The wavelength ⁇ b 3 through which the transponder wavelengths ⁇ 17 to ⁇ 19 can pass is disposed across the band of the frequencies f 17 to f 25 .
  • the bandwidths of the cAWG wavelengths of the second side port p 02 of the cAWG 24 a are disposed in the order of ⁇ b 1 , ⁇ a 2 , and ⁇ c 3 on the axis of the frequency f as follows. Specifically, the wavelength ⁇ b 1 through which the transponder wavelengths kll to ⁇ 13 can pass is disposed across the band of the frequencies f 1 to f 9 . The wavelength ⁇ a 2 through which the transponder wavelengths ⁇ 4 to ⁇ 6 can pass is disposed across the band of the frequencies f 9 to f 17 . The wavelength ⁇ c 3 through which the transponder wavelengths ⁇ 27 to 229 can pass is disposed across the band of the frequencies f 17 to f 25 .
  • the bandwidths of the cAWG wavelengths of the second side port p 03 of the cAWG 24 a are disposed in the order of ⁇ c 1 , ⁇ b 2 , and ⁇ a 3 on the axis of the frequency f as follows. Specifically, the wavelength ⁇ c 1 through which the transponder wavelengths ⁇ 21 to ⁇ 23 can pass is disposed across the band of the frequencies f 1 to f 9 . The wavelength ⁇ b 2 through which the transponder wavelengths ⁇ 14 to ⁇ 16 can pass is disposed across the band of the frequencies f 9 to f 17 . The wavelength ⁇ a 3 through which the transponder wavelengths ⁇ 7 to ⁇ 9 can pass is disposed across the band of the frequencies f 17 to f 25 .
  • Transmission paths can be changed without wavelength collision by changing the wavelengths ⁇ 1 to ⁇ 29 of optical signals transmitted from the transponders 25 a to 25 n ( FIG. 1 ).
  • the wavelength ⁇ 1 can be changed to the wavelength ⁇ 2 under wavelength change control by the monitoring control unit 21 while the transponders 25 a to 25 n are connected with the first side ports p 1 to p 3 of the cAWG 24 a .
  • the wavelength change control is instructed by the monitoring control device 15 .
  • FIG. 5 illustrates the node 11 a as a representative of the nodes 11 a to 11 d ( FIG. 1 ).
  • the monitoring control device 15 is configured as an element management system (EMS) or the like configured to manage instruments (elements) such as the nodes 11 a to 11 d included in a network.
  • EMS element management system
  • NMS network management system
  • the NMS performs processing of collecting and managing information related to equipment included in the network and settings thereof, monitoring and recording the status of data flowing in the network, the operation situation of each instrument, and the like, and giving notification to an administrator when anomaly or a presage thereof is sensed.
  • the monitoring control device 15 is disposed separately from the node 11 a in a remote manner or the like and instructs optical path generation control, wavelength change control, and the like to the monitoring control unit 21 of the node 11 a .
  • the monitoring control device 15 includes a north-bound interface (NBI) 15 a , a south-bound interface (SBI) 15 b , a path calculation unit 15 c , and a database (DB) 15 d .
  • the NBI 15 a is an interface for the higher-level device 16 .
  • the SBI 15 b is an interface for a lower-level device (in this example, the node 11 a ).
  • the DB 15 d stores a wavelength use management table 15 d 1 , a connection status management table 15 d 2 , and a usable wavelength management table 15 d 3 . These tables are also referred to as management tables 15 d 1 , 15 d 2 , and 15 d 3 .
  • the wavelength use management table 15 d 1 manages a wavelength use status of each link by the optical fibers 12 and 13 as follows. For example, it is assumed that the nodes 11 a to 11 d have link numbers # 1 , # 2 , # 3 , and # 4 as illustrated in FIG. 6 . In this case, an optical signal of the wavelength ⁇ 1 is transmitted from the node 11 a via the link # 1 and passes through the node lib. In addition, it is assumed that an optical signal of the wavelength ⁇ 3 is transmitted from the node 11 a via the link # 4 and the node 11 d and then via the link # 3 and passes through the node 11 c.
  • FIG. 7 illustrates the management table 15 d 1 that manages the wavelength use status of each of the links # 1 to # 4 in this case.
  • the management table 15 d 1 has a matrix configuration having the link numbers # 1 , # 2 , # 3 , and # 4 in columns and having the wavelength ⁇ 1 , ⁇ 2 , ⁇ 3 , ⁇ 4 , . . . in rows.
  • the management table 15 d 1 indicates that the wavelength ⁇ 1 is “in use” at the link number # 1 and “available” at the other link numbers # 2 to # 4 . It is indicated that the wavelength 22 is “available” at all link numbers # 1 to # 4 .
  • the management table 15 d 1 manages the wavelength use status of each of the links # 1 to # 4 .
  • connection status management table 15 d 2 manages the connection statuses of the add/drop unit 24 and the transponders 25 a to 25 n of each of the nodes 11 a to 11 d ( FIG. 1 ).
  • the usable wavelength management table 15 d 3 manages usable wavelengths for respective paths of the transponders 25 a to 25 n in each of the nodes 11 a to 11 d.
  • the path calculation unit 15 c performs calculation to be described later when optical path generation control, wavelength change control, or the like is requested by the higher-level device 16 through the NBI 15 a .
  • the request is also performed by a person such as the administrator.
  • the path calculation unit 15 c reads, from the management tables 15 d 1 to 15 d 3 stored in the DB 15 d , the number of available wavelengths of each link for the optical fibers 12 and 13 , the path of each of the transponders 25 a to 25 n ( FIG. 1 ), and the number of usable wavelengths, and performs calculation that allocates an optical path using available optical paths (the optical fibers 12 and 13 ) and available wavelengths based on the read information.
  • the path calculation unit 15 c sends, to the monitoring control unit 21 of each of the nodes 11 a to 11 d through the SBI 15 b in accordance with a result of the calculation, an instruction for setting a path through the nodes 11 a to 11 d and use wavelengths, such as an instruction of transmission wavelengths to the transponders 25 a to 25 n.
  • the monitoring control unit 21 sets paths and usable wavelengths of the transponders 25 a to 25 n and then sends setting change complete notification to the monitoring control device 15 .
  • the contents of the notification are stored in the management tables 15 d 1 to 15 d 3 .
  • the monitoring control device 15 thus configured can achieve a CDC function at low cost, but has constraints on wavelengths selectable for each transponder output path, depending on characteristics and connection ports of the cAWGs 24 a and 24 b connected with each of the transponders 25 a to 25 n.
  • the number of optical paths that can be accommodated decreases when simple accommodation designing that, for example, optical paths are sequentially set with priorities in ascending order of the wavelength number is performed without sufficient consideration on the connection status and optical path accommodation status of the transponders 25 a to 25 n at each of the nodes 11 a to 11 d .
  • there is another defect designing man-hour significantly increases when optical path accommodation designing is manually performed with consideration on various factors.
  • the monitoring control device 15 of the present embodiment can manage available wavelength resources and usable wavelengths at the nodes 11 a to 11 d and recommend or automatically set use wavelengths in response to a request for optical path generation and change.
  • the monitoring control device 15 may further include a node configuration management table 15 d 4 in the DB 15 d .
  • the node configuration management table 15 d 4 manages a node type that indicates whether the nodes 11 a to 11 d are each a node without the CDC function, a node of the existing CDC function, or a node including the add/drop unit 24 of the present invention.
  • a network including an existing ROADM and an existing CDC-ROADM in mixture at each of the nodes 11 a to 11 d can be achieved.
  • a network can be flexibly established in accordance with physical topology and traffic situation.
  • FIG. 9 is a block diagram illustrating specific configurations of the light SW unit 23 and the add/drop unit 24 in the light transmission system 10 of the present embodiment.
  • the light SW unit 23 includes an optical coupler 23 a interposed and connected with the one optical fiber 13 , and a wavelength selective switch (WSS) 23 b , and includes an optical coupler 23 d interposed and connected with the other optical fiber 12 , and a WSS 23 c.
  • WSS wavelength selective switch
  • the WSSs 23 b and 23 c are each an optical switch that has a wavelength multiplexing-demultiplexing function to connect a wavelength-division-multiplexed WDM signal transmitted to the optical fibers 12 and 13 with a port different for each wavelength and is capable of changing a combination of a wavelength and a port under remote control by the monitoring control device 15 .
  • the WSSs 23 b and 23 c each also have an attenuation function to adjust a transmitted light power level for each wavelength.
  • the add/drop unit 24 includes an active-system cAWG 24 c and a redundant-system cAWG 24 e that are used as an add function (add unit), and an active-system cAWG 24 d and a redundant-system cAWG 24 f that are used as a drop function (drop unit).
  • the 8 ⁇ 8 cAWGs 24 c and 24 e and the 8 ⁇ 8 cAWGs 24 d and 24 f each include the second side ports p 01 to p 04 and p 05 to p 08 and the first side ports p 1 to p 8 .
  • Transponder signals of the wavelengths ⁇ 1 to ⁇ 29 can pass through the bandwidths of the cAWG wavelengths of each of the first side ports p 1 to p 8 .
  • the bandwidth of one cAWG wavelength is 400 GHz and the channel interval of transmission bands of the eight ports p 01 to p 08 and the eight ports p 1 to p 8 on the respective input-output sides is 400 GHz. It is assumed that the bandwidth of each transponder signal is 50 GHz and the channel interval of transponder signals is 50 GHz.
  • the second side ports p 01 to p 04 are connected with a port of the WSS 23 c on the optical fiber 12 side
  • the second side ports p 05 to p 08 are connected with a port of the WSS 23 b on the optical fiber 13 side.
  • the first side port p 1 is connected with a transmission side port of the transponder 25 a
  • the first side port p 2 is connected with a transmission side port of the transponder 25 b.
  • the second side ports p 01 to p 04 are connected with the optical coupler 23 a on the optical fiber 13 side
  • the second side ports p 05 to p 08 are connected with the optical coupler 23 d on the optical fiber 12 side.
  • the first side port p 1 is connected with a reception side port of the transponder 25 a
  • the first side port p 2 is connected with a reception side port of the transponder 25 b.
  • the second side ports p 01 to p 04 are connected with a port of the WSS 23 c on the optical fiber 12 side
  • the second side ports p 05 to p 08 are connected with a port of the WSS 23 b on the optical fiber 13 side.
  • the first side port p 1 is connected with a transmission side port of the transponder 25 c
  • the first side port p 2 is connected with a transmission side port of the transponder 25 d.
  • the second side ports p 01 to p 04 are connected with the optical coupler 23 a on the optical fiber 13 side, and the second side ports p 05 to p 08 are connected with the optical coupler 23 d on the optical fiber 12 side.
  • the first side port p 1 is connected with a reception side port of the transponder 25 c
  • the first side port p 2 is connected with a reception side port of the transponder 25 d.
  • an optical signal of an optional wavelength can be transmitted or cut off between the transponders 25 a to 25 d and the optical fibers 12 and 13 through the add/drop unit 24 as follows.
  • wavelength change control of the transponders 25 a to 25 d is performed under remote control by the monitoring control device 15 .
  • the present description will be made on the active system.
  • an optical signal (transponder signal) of the wavelength ⁇ 1 is output from the transponder 25 a in a direction indicated with an arrow Y 1 a .
  • the optical signal of the wavelength ⁇ 1 is input to the port p 1 of the cAWG 24 c and output from the port p 01 to the WSS 23 c on the optical fiber 12 side.
  • the WSS 23 c transmits the optical signal of the wavelength ⁇ 1 to the fiber 12 in the direction indicated with the arrow Y 1 .
  • the WSS 23 c is controlled to cut off the wavelength ⁇ 1
  • the WSS 23 c cuts off the optical signal of the wavelength ⁇ 1 .
  • This control of transmission or cutoff at the WSS 23 c is similarly performed at the WSS 23 b on the optical fiber 13 side. Specifically, for example, an optical signal of the wavelength ⁇ 4 transmitted from the transponder 25 b , which is illustrated with an arrow Y 1 b , is transmitted to the optical fiber 13 or cut off at the WSS 23 b.
  • the optical coupler 23 a on the optical fiber 13 side bifurcates, for example, an optical signal of the wavelength ⁇ 3 transmitted through the optical fiber 13 .
  • the bifurcated optical signal of the wavelength ⁇ 3 is input through the port p 01 of the cAWG 24 d and input to the transponder 25 a through the port p 1 as illustrated with an arrow Y 1 c .
  • the optical signal of the wavelength ⁇ 3 is input to the transponder 25 b as illustrated with an arrow Y 1 d.
  • the optical coupler 23 d on the optical fiber 12 side bifurcates, for example, an optical signal of the wavelength ⁇ 4 transmitted through the optical fiber 12 .
  • the bifurcated optical signal of the wavelength ⁇ 4 is input to the port p 01 of the cAWG 24 d and input to the transponder 25 a through the port p 1 as illustrated with the arrow Y 1 c .
  • the optical signal of the wavelength ⁇ 4 is output from the port p 2 of the cAWG 24 d , the optical signal of the wavelength ⁇ 4 is input to the transponder 25 d as illustrated with the arrow Y 1 d.
  • the monitoring control unit 21 performs wavelength change control on the nodes 11 a to 11 d in accordance with a wavelength change control instruction from the monitoring control device 15 as follows. For example, it is assumed that an optical signal of the wavelength ⁇ 1 is transmitted from the transponder 25 a to the port p 1 of the cAWG 24 c as illustrated with the arrow Y 1 a .
  • the optical signal of the wavelength ⁇ 4 after the wavelength change can be transmitted to a path (the arrow Y 1 ) identical to that for the optical signal of the wavelength ⁇ 1 before the change.
  • optional transponder signals of, for example, the wavelengths ⁇ 1 to ⁇ 29 can pass through the bandwidths of transmission wavelengths of the ports p 1 to p 8 .
  • the wavelength ⁇ 1 of the optical signal from the transponder 25 a is changed to the wavelength ⁇ 4 as described above, the optical signal of the wavelength ⁇ 4 after the change is transmitted from the WSS 23 c to the same optical fiber 12 through the ports p 1 and p 01 of the cAWG 24 c like the optical signal of the wavelength ⁇ 1 before the change.
  • an optical signal from a transponder can be output at a different wavelength to the same path without change of physical wiring.
  • the optical signal of the wavelength ⁇ x after the change is transmitted from the WSS 23 b to the optical fiber 13 through the ports p 1 and p 05 of the cAWG 24 c in the direction of the arrow Y 2 .
  • the transponder wavelength ⁇ 1 in the configuration in FIG. 9 passes through the bandwidth of the cAWG wavelength ⁇ a 1 and is transmitted to the WSS 23 c through the ports p 1 and p 01 of the cAWG 24 c
  • the transponder wavelength ⁇ x passes through the bandwidth of the cAWG wavelength ⁇ a 2 and is transmitted to the WSS 23 b through the ports p 1 and p 05 of the cAWG 24 c.
  • an optical signal from a transponder can be output through an optional path, in other words, a different path without change of physical wiring.
  • An optical signal of the wavelength ⁇ 1 is output from the one transponder 25 a and transmitted to the WSS 23 c through the ports p 1 and p 01 of the cAWG 24 c as illustrated with the arrow Y 1 a .
  • An optical signal of the same wavelength ⁇ 1 is output from the other transponder 25 b and transmitted to the WSS 23 b through the ports p 2 and p 05 of the cAWG 24 c as illustrated with the arrow Y 1 b .
  • the optical signals of the same wavelength ⁇ 1 are transmitted to the optical fibers 12 and 13 as different transmission paths through the different ports of the cAWG 24 c , and thus do not collide.
  • FIG. 10 is a block diagram illustrating other specific configurations of a light SW unit 23 A and an add/drop unit 24 A in the light transmission system 10 of the present embodiment.
  • the light SW unit 23 A illustrated in FIG. 10 is different from the light SW unit 23 ( FIG. 9 ) described above in that the light SW unit 23 A only includes the optical couplers 23 a and 23 d .
  • the add/drop unit 24 A is different from the add/drop unit 24 ( FIG. 9 ) described above in that the add/drop unit 24 A includes optical couplers 23 h , 23 i , 23 j , and 23 k in addition to the cAWGs 24 c and 24 e and the cAWGs 24 d and 24 f .
  • the cAWGs 24 c and 24 e and optical couplers 24 h to 24 k connected with the ports p 01 and p 02 thereof are combined to achieve an add function.
  • the cAWGs 24 d and 24 f and optical couplers 24 i and 24 j connected with the ports p 01 and p 02 thereof are combined to achieve a drop function.
  • these cAWGs are also referred to as AWGs 24 c and 24 e of the add function and AWGs 24 d and 24 f of the drop function.
  • the optical coupler 23 a connected with the optical fiber 13 in the light SW unit 23 A is connected with the optical couplers 23 h and 23 i in the add/drop unit 24 A.
  • the optical coupler 23 d connected with the optical fiber 12 is connected with the optical couplers 23 j and 23 k .
  • the optical coupler 23 h is connected with the second side ports p 01 of the cAWG 24 c and 24 e .
  • the optical coupler 23 i is connected with the second side ports p 01 of the cAWG 24 d and 24 f .
  • the optical coupler 23 j is connected with the second side ports p 02 of the cAWG 24 d and 24 f .
  • the optical coupler 23 k is connected with the second side ports p 02 of the cAWG 24 c and 24 e.
  • wavelength change control of the transponders 25 a to 25 d is performed under remote control by the monitoring control device 15 .
  • the present description will be made on the active system.
  • an optical signal of the wavelength ⁇ 1 is output from the transponder 25 a in the direction indicated with the arrow Y 1 a .
  • the optical signal of the wavelength ⁇ 1 is input to the port p 1 of the cAWG 24 c of the add function and output from the port p 01 through the optical coupler 24 h and the optical coupler 23 a to the optical fiber 13 in the direction of the arrow Y 2 .
  • an optical signal of the wavelength ⁇ 3 transmitted through the optical fiber 13 is input to the optical coupler 23 a on the optical fiber 13 side.
  • the optical signal is bifurcated at the optical coupler 23 a , input to the port p 01 of the cAWG 24 d of the drop function through the optical coupler 24 i , and further input from the port p 1 to the transponder 25 a as illustrated with the arrow Y 1 c .
  • the optical signal of the wavelength ⁇ 3 is output from the port p 2 of the cAWG 24 d
  • the optical signal of the wavelength ⁇ 3 is input to the transponder 25 b as illustrated with the arrow Y 1 d.
  • an optical signal of the wavelength ⁇ 1 is output from the transponder 25 b in a direction indicated with the arrow Y 1 b .
  • the optical signal of the wavelength ⁇ 1 is input to the port p 2 of the cAWG 24 c of the add function and output from the port p 02 through the optical coupler 24 k and the optical coupler 23 d to the optical fiber 12 in the direction of the arrow Y 1 .
  • an optical signal of the wavelength 23 transmitted through the optical fiber 12 is input to the optical coupler 23 d on the optical fiber 12 side.
  • the optical signal is bifurcated at the optical coupler 23 d , input from the port p 02 of the cAWG 24 d through the optical coupler 24 j , and further input from the port p 1 to the transponder 25 a as illustrated with the arrow Y 1 c .
  • the optical signal of the wavelength 23 is output from the port p 2 of the cAWG 24 d
  • the optical signal of the wavelength 23 is input to the transponder 25 b as illustrated with the arrow Y 1 d.
  • the monitoring control unit 21 performs wavelength change control on the nodes 11 a to 11 d in accordance with a wavelength change control instruction from the monitoring control device 15 as follows. For example, it is assumed that an optical signal of the wavelength ⁇ 1 is transmitted from the transponder 25 a to the optical couplers 24 h and 23 a through the ports p 1 and p 01 of the cAWG 24 c as illustrated with the arrow Y 1 a .
  • the optical signal of the wavelength ⁇ 4 after the wavelength change can be transmitted to a path (arrow Y 2 ) identical to that for the optical signal of the wavelength ⁇ 1 before the change because of transmission characteristics of the cAWG 24 c.
  • optional transponder signals of, for example, the wavelengths ⁇ 1 to ⁇ 29 can pass through the bandwidths of transmission bands of the ports p 1 to p 8 .
  • the wavelength ⁇ 1 of the optical signal from the transponder 25 a is changed to the wavelength ⁇ 4 as described above, the optical signal of the wavelength ⁇ 4 after the change is transmitted to the same optical fiber 13 through the ports p 1 and p 01 of the cAWG 24 c and the optical couplers 24 h and 23 a like the wavelength ⁇ 1 before the change.
  • an optical signal from a transponder can be output at a different wavelength to the same path without change of physical wiring.
  • the cAWG 24 c has a characteristic that the wavelength ⁇ x is output from the port p 02 when input through the port p 1
  • the optical signal of the wavelength ⁇ x after the change is transmitted through the ports p 1 and p 02 of the cAWG 24 c and the optical couplers 24 k and 23 d to the optical fiber 12 in the direction of the arrow Y 1 .
  • an optical signal from a transponder can be output through an optional path, in other words, a different path without change of physical wiring.
  • An optical signal of the wavelength ⁇ 1 is transmitted from the one transponder 25 a and output to the optical couplers 24 h and 23 a through the ports p 1 and p 01 of the cAWG 24 c as illustrated with the arrow Y 1 a .
  • An optical signal of the same wavelength ⁇ 1 is transmitted from the other transponder 25 b and output to the optical couplers 24 k and 23 d through the ports p 2 and p 02 of the cAWG 24 c as illustrated with the arrow Y 1 b .
  • the optical signals of the same wavelength ⁇ 1 are transmitted to the optical fibers 12 and 13 as different transmission paths through the different ports p 01 and p 02 of the cAWG 24 c , and thus do not collide.
  • the optical add/drop multiplexer drops or adds an optical signal between the optical add/drop multiplexer and each of the transponders 25 a to 25 n connected with the communication terminals 31 a to 31 n , the optical signal being transmitted by wavelength division multiplexing to a light transmission path included in a communication network.
  • the optical add/drop multiplexer includes a plurality of first side ports and a plurality of second side ports connected between each of the transponders 25 a to 25 n and the light transmission path.
  • a first channel interval of each of the first and second side ports is a plurality of times larger than a second optical signal input-output channel interval of ports of the transponders 25 a to 25 n .
  • the optical add/drop multiplexer includes the cAWGs 24 a and 24 b in which optical signals of a plurality of different wavelengths from one or a plurality of the transponders 25 a to 25 n or the light transmission path can pass through a first channel.
  • the cAWGs 24 a and 24 b each cause an optical signal from each of the transponders 25 a to 25 n to pass through the first channel at one of the first side ports.
  • the cAWGs 24 a and 24 b each output and transmit the passing optical signal to the light transmission path in a cyclic relation determined in accordance with a corresponding second side port among the plurality of second side ports and the wavelength of the output optical signal from the transponder.
  • the cAWGs 24 a and 24 b each cause the optical signal transmitted through the light transmission path to pass through the first channel at one of the second side ports.
  • the cAWGs 24 a and 24 b each output the passing optical signal to the corresponding one of the transponders 25 a to 25 n in a cyclic relation determined in accordance with the first side port among the plurality of first side ports and the wavelength of the output optical signal from the transponder.
  • one or transponder signals of a plurality of different wavelengths can pass through channels at the first and second side ports of the cAWG.
  • the wavelength (for example, a wavelength ⁇ 1 ) of a transponder signal from each of the transponders 25 a to 25 n is changed to another wavelength ⁇ 4 , similarly to the transponder signal of the wavelength ⁇ 1 before the change, the transponder signal of the wavelength ⁇ 4 after the change can be transmitted to an identical light transmission path through the first and second side ports of the cAWGs 24 a and 24 b .
  • transponder signals as optical signals from the transponders 25 a to 25 n can be output at optional wavelengths to the same path without change of physical wiring between the optical add/drop multiplexer and each of the transponder devices 25 a to 25 n .
  • the optical add/drop multiplexer of the present invention does not include a multicast switch nor an amplifier configured to compensate light loss, which leads to reduction of device cost and electric power consumption.
  • the light SW unit 23 configured to transmit or cut off, when the light transmission path includes a different light transmission path, an optical signal between the different light transmission path and each of the cAWGs 24 a and 24 b is provided.
  • the wavelength of a transponder signal from each of the transponders 25 a to 25 n is changed to a different wavelength
  • the light SW unit 23 transmits an optical signal including the transponder signal of the changed wavelength to both or one of different light transmission paths.
  • an optical signal from each of the transponders 25 a to 25 n can be output through an optional path, in other words, a different path without change of physical wiring between the optical add/drop multiplexer and each of the transponder devices 25 a to 25 n.
  • the light SW unit 23 transmits, to different light transmission paths, transponder signals having an identical wavelength, transmitted from the different transponders 25 a to 25 n , and having passed through the first channels at the different cAWGs 24 a and 24 b.
  • output from a path different from an existing path can be performed at the same wavelength from the different transponders 25 a to 25 n without change of physical wiring between the optical add/drop multiplexer and each of the transponder devices 25 a to 25 n.
  • FIG. 11 is a block diagram illustrating a first port number increasing configuration of the add and drop units including cAWGs, optical couplers, and the like in the add/drop unit in the light transmission system.
  • the configuration of an add/drop unit 24 B illustrated in FIG. 11 is different from the configuration of the add/drop unit 24 ( FIG. 9 ) in that a 1 ⁇ 2 (or 1 ⁇ N) optical coupler 24 m is connected between the first side port p 1 of the cAWG 24 c and the transponder 25 a and a 1 ⁇ 2 optical coupler 24 n is connected between the first side port p 1 of the cAWG 24 d and the transponder 25 b (increasing design 1 ).
  • a 1 ⁇ N optical coupler 24 q is connected between the first side the port p 2 of the cAWG 24 e and the transponder 25 c through an optical amplifier 24 o
  • a 1 ⁇ N optical coupler 24 r is connected between the first side the port p 2 of the cAWG 24 f and a transponder 25 r through an optical amplifier 24 p (increasing design 2 ). Only the increasing design 1 or the increasing design 2 may be implemented in the configuration of the add/drop unit 24 B in FIG. 11 .
  • the cAWGs 24 c and 24 e and the optical couplers 24 m and 24 q connected with the ports p 1 and p 2 thereof are combined to achieve an add function (add unit).
  • the cAWGs 24 d and 24 f and the optical couplers 24 n and 24 r connected with the ports p 1 and p 2 thereof are combined to achieve a drop function (drop unit).
  • the number of possible connections of the transponders 25 a to 25 d illustrated in FIG. 9 depends on the number of cAWG ports of the cAWGs 24 c and 24 e and the cAWGs 24 d and 24 f .
  • the number of transponders connectable with the add/drop unit 24 B has a limitation.
  • the 1 ⁇ N optical couplers 24 m to 24 r are connected between the first side port p 1 or p 2 of the corresponding one of the cAWGs 24 c and 24 e and the cAWGs 24 d and 24 f and the corresponding one of the transponders 25 a to 25 d as described above.
  • the optical couplers 24 m to 24 r each have 1 ⁇ 2 ports, two of the transponders 25 a to 25 d can be connected with one port p 1 or p 2 of the corresponding one of the cAWGs 24 c and 24 e and the cAWGs 24 d and 24 f.
  • transponders can be connected in a number two times larger than that for the configuration of connection with the cAWGs 24 c and 24 e and the cAWGs 24 d and 24 f illustrated in FIG. 9 .
  • wavelengths in a number Wx equal to “AWG channel interval/channel interval of transponder output optical signals ⁇ 1” can be input to the ports p 1 to p 8 in effective.
  • the upper limit value of an effective number of connectable transponders is “the wavelength number Wx ⁇ the number of AWG ports”.
  • large signal loss occurs through N bifurcations at the optical couplers 24 q and 24 r .
  • an optical signal attenuates to a predetermined value or lower.
  • the amplifiers 24 o and 24 p are each connected between the port p 2 of the corresponding one of the cAWGs 24 e and 24 f and the corresponding one of the two 1 ⁇ N optical couplers 24 q and 24 r , thereby achieving signal amplification to solve the signal loss.
  • FIG. 12 is a block diagram illustrating a second port number increasing configuration of the add and drop units including cAWGs in the add/drop unit in the light transmission system.
  • the configuration of an add/drop unit 24 C illustrated in FIG. 12 is different from the configuration of the add/drop unit 24 illustrated in FIG. 9 in that, in addition to the cAWG 24 c in existing connection, a cAWG 24 c 1 is connected in parallel with the WSSs 23 c and 23 b interposed in the respective optical fibers 12 and 13 . It is assumed that the cAWGs 24 c and 24 e , the cAWGs 24 d and 24 f , and the cAWG 24 c 1 each have four second side ports p 01 , p 02 , p 0 3 , and p 04 .
  • a port transmission wavelength (target wavelength ⁇ j) of the cAWG 24 c 1 as a connection target has a plurality of relations as illustrated in FIG. 13 with a port transmission wavelength (reference wavelength ⁇ k) of the cAWG 24 c in existing connection.
  • the first relation is a relation in which a central frequency fj 1 of the target wavelength ⁇ j 1 indicated by Reference Sign 1 in FIG. 13 is adjusted to a central frequency fk of the reference wavelength ⁇ k indicated by Reference Sign 0 .
  • the second relation is a relation in which a central frequency fj 2 of a target wavelength ⁇ j 2 indicated by Reference Sign 2 is shifted by half wavelength relative to the central frequency fk of the reference wavelength ⁇ k.
  • the third relation is a relation in which a central frequency fj 3 of a target wavelength ⁇ j 3 indicated by Reference Sign 3 is shifted by one wavelength relative to the central frequency fk of the reference wavelength ⁇ k.
  • the target wavelength ⁇ j may have both characteristics of the second relation and the third relation.
  • FIG. 14 is a block diagram illustrating a mixed configuration of a single carrier optical path and a multi carrier optical path in the light transmission system.
  • 1 ⁇ 2 optical couplers 24 s and 24 t are additionally connected with the first side ports p 1 of the cAWGs 24 c and 24 d (first additional configuration).
  • 1 ⁇ 4 optical couplers 24 q and 24 r are additionally connected with the first side ports p 1 of the cAWGs 24 e and 24 f through optical amplifiers 24 o and 24 p (second additional configuration).
  • the cAWGs 24 c and 24 e and the optical couplers 24 s and 24 t connected with the ports p 1 thereof are combined to achieve an add function.
  • the AWGs 24 d and 24 f and the optical couplers 24 q and 24 r connected with the ports p 1 thereof are combined to achieve a drop function.
  • a multi carrier optical path transponder 25 f including two transmission ports p 11 and p 12 and two reception ports p 13 and p 14 is connected with the above-described connected 1 ⁇ 2 optical couplers 24 s and 24 t .
  • a multi carrier optical path transponder 25 g including four transmission ports p 21 , p 22 , p 23 , and p 24 and four reception ports p 25 , p 26 , p 27 , and p 28 is connected with the above-described connected 1 ⁇ 4 optical couplers 24 q and 24 r .
  • single carrier optical path transponders 25 h are connected with one port (for example, the port p 2 ) in the first side ports p 1 to p 8 of the cAWGs 24 c and 24 e and one port (for example, the port p 2 ) in the first side ports p 1 to p 8 of the cAWGs 24 d and 24 f.
  • a multi carrier optical signal M 1 in which an optical signal of the wavelength ⁇ 1 and an optical signal of the wavelength ⁇ 2 illustrated in FIG. 15 are superimposed is transmitted from the two transmission ports p 11 and p 12 of the multi carrier optical path transponder 25 f .
  • the transmitted multi carrier optical signal M 1 is input to the port p 1 of the cAWG 24 c of the add function through the optical couplers 24 s and 24 h .
  • the transmitted multi carrier optical signal M 1 is output from the port p 01 of the cAWG 24 c and transmitted through the WSS 23 c to the optical fiber 12 in the direction of the arrow Y 1 .
  • a multi carrier optical signal (refer to the multi carrier optical signal M 1 in FIG. 15 ) bifurcated at the optical coupler 23 a on the optical fiber 13 side is input to the port p 01 of the cAWG 24 d of the drop function and input from the port p 1 to the reception ports p 13 and p 14 of the transponder 25 f through the optical coupler 24 t.
  • a single carrier optical signal (not illustrated) of the wavelength ⁇ 3 is transmitted from a transmission port of the single carrier optical path transponder 25 h and input to a port (for example, the port p 2 ) of the cAWG 24 c other than the multi carrier optical path.
  • a single carrier optical signal bifurcated at the optical coupler 23 a on the optical fiber 13 side is input to a reception port of the transponder 25 h through the ports p 02 and p 2 of the cAWG 24 d.
  • a multi carrier optical signal M 2 (refer to the multi carrier optical signal M 1 in FIG. 15 ) in which two optical signal (not illustrated) of wavelengths ⁇ 41 and ⁇ 42 are superimposed may be transmitted from the two transmission ports p 11 and p 12 of the transponder 25 f .
  • the transmitted multi carrier optical signal M 2 can be transmitted through the optical coupler 24 s , the ports p 1 and p 05 of the cAWG 24 c , and the WSS 23 b to the optical fiber 13 in the direction of the arrow Y 2 .
  • the single carrier optical path and the multi carrier optical path can be provided in mixture.
  • a multi carrier optical signal M 3 in which optical signals of the four wavelengths ⁇ 1 to ⁇ 4 (not illustrated) are superimposed can be transmitted from the four transmission ports p 21 to p 24 of the other multi carrier optical path transponder 25 g .
  • the transmitted multi carrier optical signal M 3 is input to the port p 1 of the cAWG 24 e of the add function through the optical coupler 24 q .
  • the multi carrier optical signal M 3 is output from, for example, the port p 05 of the cAWG 24 e and transmitted through the WSS 23 b to the optical fiber 13 in the direction of the arrow Y 2 .
  • a signal (refer to the multi carrier optical signal M 3 ) of a larger number of wavelengths can be input to a port of an identical cAWG (refer to the cAWG 24 e ) by transmitting the multi carrier optical signal M 3 in which optical signals of the four wavelengths ⁇ 1 to ⁇ 4 are superimposed, and thus large-volume data transmission can be performed through one path.
  • a multi carrier optical signal M 4 in which optical signals of the two wavelengths ⁇ 1 and ⁇ 2 (not illustrated) are superimposed may be transmitted from two ports p 21 and P 22 among the four transmission ports p 21 to p 24 of the transponder 25 g
  • a multi carrier optical signal M 5 in which optical signals of the two wavelengths ⁇ 41 and ⁇ 42 (not illustrated) are superimposed may be transmitted from the other two ports p 23 and P 24 .
  • the multi carrier optical signals M 4 and M 5 are input to the port p 1 of the cAWG 24 e through the optical coupler 24 q .
  • the input multi carrier optical signal M 4 is transmitted through the WSS 23 b to the optical fiber 13 in the direction of the arrow Y 2 .
  • the input multi carrier optical signal M 5 is transmitted through the WSS 23 c to the optical fiber 12 in the direction of the arrow Y 1 .
  • FIG. 16 is a block diagram illustrating the configuration of a guard function and a monitoring function in the light transmission system of the present embodiment.
  • any component illustrated in FIG. 10 is denoted by the same reference sign, and description thereof is omitted.
  • an optical amplifier 23 f is connected with an input side of the optical coupler 23 a on the optical fiber 13 side in a light SW unit 23 B, an optical amplifier 23 g is connected with an output side thereof, the optical amplifier 23 i is connected with an input side of the optical coupler 23 d on the optical fiber 12 side, and the optical amplifier 23 h is connected with an output side thereof.
  • the paths are a clockwise path from one side to the other side, which is illustrated with the arrow Y 1 , and a anticlockwise path from the other side to the one side, which is illustrated with the arrow Y 2 .
  • Each path is connected with the transponder 25 a through the optical couplers 23 a and 23 d and the cAWG 24 a .
  • Each path is also connected with an opposite side transponder (not illustrated) configured to perform communication with the transponder 25 a through the optical fibers 12 and 13 .
  • an optical signal is potentially output to an unintentional path and causes a penalty due to collision and crosstalk with another optical signal.
  • the above-described penalty potentially occurs when the transponder 25 a is changed to the different wavelength ⁇ 4 at change from the wavelength ⁇ 1 to the wavelength ⁇ 2 for some reason.
  • the monitoring control unit 21 monitors input power and the number of input wavelengths of the optical amplifiers 23 f to 23 i connected with the input and output sides of the optical couplers 23 a and 23 d interposed in the optical fibers 12 and 13 .
  • the monitoring control unit 21 stops output from the transponder 25 a when the monitored input power or number of input wavelengths deviates by a predetermined value or more from input power or the number of input wavelengths included in path setting information of path generation control, which is instructed by the monitoring control device 15 . In this case, output from the opposite side transponder for the transponder 25 a is stopped as necessary. Accordingly, it is possible to prevent an optical signal from being output to a different path and causing a penalty due to collision and crosstalk with another optical signal when the output wavelength of the transponder 25 a is unintentionally changed as described above.
  • a reception unit of the transponder 25 a may notify the monitoring control unit 21 of this error information so that the monitoring control unit 21 stops outputs from the transponder 25 a and the opposite side transponder.

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